I have a friend, we share a birthday, but he is born one year later. We are so totally alike in mind, I can predict what he is going to say, or the joke he is going to make in conversation. I thought about whether or not I would want to take our friendship a step further, but I decided not to because I would get annoyed with the downsides of my/our character. And if I can predict what the other is going to say in conversation, then I don't need to have the conversation anymore.